This invention concerns auxiliary axle assemblies which have been used to augment the load carrying ability of vehicles, when heavily loaded or when towing a trailer. Many such xe2x80x9ctagxe2x80x9d axles have been devised in the past.
A prime consideration has been the effect such auxiliary axles have on steering. The prior designs typically create tire scrubbing when turning due to the fact that the inside and outside wheels do not align with the radius of the turn since the axle wheels are constrained by their mounting to the axle to remain in alignment with each other rather than to align with the turn radius.
When used to tow a trailer, the trailer load often results in bending forces being imposed on the tag axle frame which can become excessive particularly on a rough road.
Many of the prior tag axle designs are bulky and complicated and create instability when used to tow a vehicle.
It is the object of the present invention to provide a simple and compact auxiliary axle assembly which contributes to vehicle stability in turns and which assumes a controllable proportion of the towed vehicle load without being subjected to excessive bending stress.
The above recited object and others which will become apparent upon a reading of the following specification and claims are accomplished by an auxiliary axle assembly comprising a central frame member preferably comprising a square tube piece having a pair of downwardly inclined swing arms each pivotally supported on one side of the frame and normally inclined to trail to the rear. The outer end of each swing arm mounts a wheel-tire assembly including wheel bearings for rotational support thereof.
A selectively pressurizable air spring is pivotally mounted at one end to each swing arm and at the other end to a bracket fixed to the frame member to support each swing arm under the weight of the supported load.
A hitch is welded to an attachment plate, which is adjustably mounted to a forward end of the frame member.
The hitch is adjusted to the approximate height of the hitch receiver of the towing vehicle, and the air springs pressurized to a level accurately aligning the hitch and hitch receiver and enable mounting thereof.
When the vehicle is loaded, the air springs are pressurized to raise the vehicle and axle to its normally unloaded height to insure proper steering and cause the auxiliary axle to partially. assume the vehicle load.
The auxiliary axle assembly when so loaded has been found to track the steering radius by relative movement of the respective swing arms to align the wheels along the radius of the turning arc to eliminate tire scrubbing and improve vehicle stability.
This simple rugged and compact design can be easily and quickly installed and manufactured at low cost.